Merge pull request #57 from miniway/master

ew timer during handling timer_event doesn't set correctly
ZMsg.recv documentation of flag options
Merge pull request #63 from xekoukou/master

small documentation change
Add chapter 5 guide
fix missing frame at monitoring

But monitoring will be totally rewritten
add a pom helper for the latest sonatype snapshot
add setTCPKeepAlive socket option
Fix a bug that socket disconnect didn't terminate properly